The present invention relates to an excavator arm configured to equip an excavator. Besides, the present invention relates to an excavator cantilever member including such an excavator arm. Furthermore, the present invention relates to an excavator including such an excavator cantilever member.
The invention can be applied in construction equipment machines, such as mechanical shovels or drillers and any other type of excavator. Such excavator may be a tracked swilling excavator comprising either a caterpillar track or wheels, and a cantilever member coupled to a rotating platform mounted on the caterpillar track. The invention can be applied also to wheeled excavators and or to backhoe loaders. Although the invention will be described with respect to a mechanical shovel, the invention is not restricted to this particular construction equipment, but may also be used in other construction equipment machines.
WO 13114451A1 discloses an excavator arm including an arm linear actuator and an electric motor driving the arm linear actuator. However, the electric motor is located on the outer region of the excavator arm, that is the region which is oriented away from the excavator cab when the excavator cantilever member is folded.
Such a location of the electric motor entails a risk of impact against external, surrounding objects on the jobsite. In order to decrease such a risk, the excavator arm of W013114451A1 has a casing designed to protect the electric motor and the major part of the arm linear actuator.
Yet, such a casing cannot protect the electric motor against any big impact. Furthermore, such a casing must be bulky and heavy, thus increasing the overall footprint of the excavator arm and the electricity consumption for operating the excavator.
It therefore appears that, from several standpoints, there is room for improvement in the excavator arm of an excavator.
It is desirable to provide an excavator arm having a light and compact design and nonetheless suitable for preventing the risk of impact of the electric motor against external, surrounding objects on the jobsite.
According to an aspect of the invention, an excavator arm, configured to equip an excavator, is provided said excavator arm including at least:
a frame comprising i) a boom linkage part configured to swingably link said excavator arm to an excavator boom about a boom axis, and ii) a tool linkage part configured to swingably link said excavator arm to a tool about a tool axis, said boom axis and said tool axis substantially extending in a frame plane,
an arm linear actuator extending substantially along a longitudinal axis, said arm linear actuator having i) a proximal linkage part linked to said frame about a proximal linkage axis and ii) a distal linkage part linked to said frame about a distal linkage axis, said proximal linkage axis and said distal linkage axis extending substantially in an actuator plane, and
an electric motor configured to drive said arm linear actuator, wherein said electric motor is arranged on the side of said frame plane with respect to said actuator plane.
Throughout the present application, the adjective “proximal” pertains to an element which is relatively close to an upper swing unit of the excavator, whereas the adjective “distal” pertains to an element which is relatively far from the upper swing unit. Hence, a proximal part of the excavator arm is closer to the upper swing unit than a distal part of the excavator arm.
By the provision of such an excavator arm, the advantage is that the electric motor is protected from any impact on the jobsite, while the excavator arm can be compact and light compared to the excavator arm of W013114451A1.
The tool linked to the excavator arm can be any kind of tool usually implemented on mechanical construction equipment. For instance, the tool can be selected from the group including a bucket, a drilling tool, a hammer and a gripping tool. Such tools can be attached to the excavator arm via an appropriate link configured to provide a quick coupling, be it hydraulic, electric and/or mechanic, between the excavator arm and the tool. Usually, the tool is mounted at the tip of the excavator arm.
According to a variant, said arm linear actuator comprises a reversible mechanical linear actuator. For instance said arm linear actuator can comprise a ball screw, a roller screw or a buttress thread screw, the screw imparting translation to a linear actuator rod by a nut. Such a mechanical linear actuator can be maintained in any given position, regardless of the forces applied thereon, by simply stopping its drive by the electric motor, whereas hydraulic linear actuators of the prior art require several cumbersome check valves to be maintained in a given position. Besides, a reversible mechanical linear actuator has the ability to recover energy when load is driving the movement. Furthermore, a reversible mechanical linear actuator avoids the transfer of excessive mechanical load to the structure of the excavator.
Alternatively, said arm linear actuator can comprise an irreversible mechanical linear actuator.
As the arm linear actuator can be driven by the electric motor, it can reach very accurate positions, produce a high torque and exert the same force during a pulling step as during a pushing step, unlike a hydraulic linear actuator of most prior art excavator arms.
According to an embodiment, said electric motor is substantially arranged between said frame plane and said actuator plane.
Throughout the present application, the term “substantially arranged” means that the electric motor can be i) either entirely arranged between frame plane and actuator plane, ii) or mostly arranged between frame plane and actuator plane while part of the electric motor is located beyond the frame plane or beyond the actuator plane.
According to an embodiment, said proximal linkage part is located at a first end portion of said arm linear actuator, and wherein said distal linkage part is located at a second end portion of said arm linear actuator.
Thus, such locations of the proximal and distal linkage parts permit to use the arm linear actuator at its full length, hence with a maximal strength.
According to an embodiment, the excavator arm further comprises a gearbox configured to transmit power from said electric motor to said arm linear actuator, said gearbox being located at said proximal linkage part.
Thus, such a gearbox permits to control the power applied from the electric motor to the arm linear actuator.
According to an embodiment, said electric motor extends along a motor axis which is substantially parallel to said longitudinal axis, and wherein said gearbox is located at said proximal linkage part.
Thus, such an arrangement of the electric motor, along the arm linear actuator, permits the excavator arm to be compact in a lateral direction.
According to an embodiment, said motor axis and said longitudinal axis extend on both sides (right and left sides) of a median plane which contains said longitudinal axis and which is perpendicular to said actuator plane. Possibly, said motor axis and said longitudinal axis can extend symmetrically with respect to said median plane.
Thus, such an arrangement of the electric motor, in the middle of the excavator arm, permits the excavator arm to be very compact in a lateral direction, perpendicular to the median plane.
Alternatively, the electric motor can be offset with respect to the median plane. In other words, the electric motor can be arranged on a side of the excavator arm.
According to an embodiment, said proximal linkage axis is transversal to said longitudinal axis, wherein said distal linkage axis is transversal to said longitudinal axis.
Thus, such proximal and distal linkage axes permit a simple construction and maneuver of the excavator arm.
According to a variant, said proximal linkage axis is perpendicular to said longitudinal axis, and said distal linkage axis is perpendicular to said longitudinal axis.
According to an embodiment, said frame defines a cavity which opens on at least one side, said electric motor being at least partly received in said at least one cavity.
Such a cavity is defined by some walls or plates of the frame. For instance, the cavity can be defined by the first and second side plates and by the lower plate.
Advantageously, the frame defines a cavity in which is received at least 50%, preferably 80%, most preferably 100%, of the volume of the electric motor, and possibly of the volume of a gearbox.
Thus, such an open structure permits easy check, repair and replacement of the arm linear actuator or of the said electric motor.
According to an alternative embodiment, said frame has a generally closed structure encasing at least said arm linear actuator and said electric motor.
According to an embodiment, said frame comprises at least:
a first side plate and a second side plate located respectively on each side of said electric motor, said first side plate and said second side plate extending at least from said boom linkage part to said tool linkage part, and
a proximal stiffener transversally joining said first side plate and said second side plate, said proximal stiffener extending from a boom connection part which is configured for connecting a boom linear actuator fastened to the excavator boom, and
a distal stiffener transversally joining said first side plate and said second side plate, said distal stiffener extending substantially from said tool axis and substantially parallel to said arm linear actuator.
Thus, the proximal stiffener can provide a high mechanical strength to a proximal portion of the excavator arm.
Likewise, the distal stiffener extending along or parallel to the line of action of the arm linear actuator provides a high mechanical strength to a distal portion of the excavator arm, since the distal stiffener extends along or parallel to the line of action of the arm linear actuator.
According to an embodiment, said proximal stiffener extends along a direction parallel to a line connecting said boom connection part to said boom axis. Thus, the proximal stiffener provides a high mechanical strength to a proximal portion of the excavator arm, since the proximal stiffener extends along or parallel to the line of action of the boom linear actuator.
According to an embodiment, said proximal stiffener transversally joins said first side plate and said second side plate, at least a part of said proximal stiffener forming a substantially closed hollow box.
Thus, such a shape can provide the proximal stiffener with a high ratio of its quadratic moments to its weight.
The proximal stiffener can have a plate-like extension protruding from said substantially closed hollow box. Advantageously, said substantially closed hollow box can have the general shape of a triangle.
In particular, said proximal stiffener can have a triangular portion located near said boom connection part, and a cantilever portion located away from said boom connection part.
According to an embodiment, said distal stiffener joins said first side plate and said second side plate, said distal stiffener substantially defining a closed hollow structure with said lower plate.
According to a variant, said distal stiffener has a length ranging from 30% to 70% of the length measured between the tool axis and the boom axis.
Thus, such a shape can provide the distal stiffener with a high ratio of its quadratic moments to its weight.
According to an embodiment, said frame further comprises a lower plate extending between said first side plate and said second side plate, for instance from said first side plate to said second side plate, such that said electric motor is located between said lower plate and said arm linear actuator.
Thus, such a lower plate reinforces the mechanical strength of the excavator arm, in particular by increasing its quadratic moment about a lateral direction. Furthermore, such a lower plate protects the electric motor from under the excavator arm against external, surrounding objects.
According to an embodiment, said first side plate and said second side plate have symmetrical shapes with respect to a median plane which contains said longitudinal axis and which is perpendicular to said actuator plane.
Thus, such symmetrical first and second side plates can provide the excavator arm with a uniform mechanical strength.
According to an embodiment, said first side plate and said second side plate have:
respective proximal portions extending relatively close to the boom axis,
respective distal portions extending relatively close to the tool axis, and                respective intermediate portions extending between said respective proximal portions and said respective distal portions,        
wherein a distal width measured between said respective distal portions is smaller than a proximal width measured between said respective proximal portions, said respective intermediate portions forming a narrowing, preferably tapered, cross-section of said frame.
Thus, such proximal, intermediate and distal portions provide the excavator arm with a uniform mechanical strength, while maintaining a low weight.
According to a variant of the invention, said first side plate, said second side plate, said proximal stiffener and said distal stiffener are metallic, preferably made of steel.
According to a variant of the invention, the proximal portions are higher than the distal portions the height being measured substantially perpendicular to the frame plane. A height ratio of the proximal portions to the distal portions can range from 2 to 4.
According to another aspect of the invention, an excavator cantilever member is provided including at least an excavator boom and an excavator arm according to the present invention, said excavator boom and said excavator arm being swingably linked about said boom axis, said excavator boom being configured such that a tip portion of said excavator boom is arranged, along said boom axis, between said first side plate and said second side plate.
In other words, the excavator arm forms a clevis mounting, or a fork joint, for the excavator boom. The side plates of the excavator boom are partially covered respectively by the first side plate and the second side plate.
Thus, such a clevis mounting permits to reduce the lateral footprint of the boom.
According to an embodiment, the tool is a bucket, said bucket being linked to said excavator arm.
According to another aspect of the invention, an excavator is provided including a lower driving unit, an upper swing unit turnably mounted on the lower driving unit and an excavator cantilever member, wherein said excavator cantilever member includes at least an excavator boom and an excavator arm according to the present invention, said excavator boom being swingably mounted to the upper vehicle unit.
Thus, such an excavator can have an excavator arm equipped with an electric motor, which is fully protected from impact against outer objects while providing some advantages. For instance, the linear actuator can exert the same force during a pulling step as during a pushing step, unlike a hydraulic linear actuator where the piston rod impinges on the cross-section area of the piston rod chamber but not on the cross-section area of the bottom chamber.
Within the scope of the present invention, the afore-mentioned embodiments and variants can be considered either in isolation or in any technically possible combination.